Quantum state tomography of 1D resonance fluorescence

Abstract

Tomography is the name under which all state reconstruction techniques are denoted, one of the most recognized examples being medical tomography. Quantum state tomography is a procedure to determine the quantum state of a physical system. By performing homodyne measurements on resonance fluorescence from an artificial atom coupled to a one-dimensional transmission line, its quantum state can be reconstructed. Resonance fluorescence is one of the simplest setups that results in non-classical states of light. If these states are non-classical in the sense that they have a negative Wigner function, they can be used as a computational resource for quantum computing. There are many different approaches to quantum computing. Some, like gate based quantum computing using discrete variables like qubits, have been extensively researched, both theoretically and experimentally. There exists and alternative approach: continuous variable quantum computing. The continuous variables we will be concerned with are the components of the electromagnetic field that constitute the resonance fluorescence. There are different parameters that affect the nature of the resonance fluorescence, for example, the number of transmission lines the atom is coupled to, or the strength of the driving field. In this work, we develop the tools necessary to numerically simulate homodyne detection of resonance fluorescence for different sets of parameters, and reconstruct the quantum state as well as calculating the Wigner negativity.